The present invention relates to a tire testing system that positions a rotating tire on a roadway simulator. More particularly, the present invention provides a lateral position control feature for a tire tread wear test machine.
The testing of tires using a roadway simulator such as a drum or flat belt is known. During the testing, the tire is rotated against an outer surface of the roadway simulator that simulates various road pavements such as concrete or blacktop. The tire is typically mounted to a wheel assembly, the wheel assembly being forced toward the roadway simulator in order to apply radial loads upon the tire to simulate the weight of an automobile.
The wheel assembly is mounted to an adjustable carriage for adjusting the axial position of the wheel assembly, and thus, when and with what force the tire contacts the roadway simulator. By varying the angular placement of the tire on the roadway simulator, tread wear, static and dynamic forces and moments, and other parameters required by specific testing practices can be measured. An example of a tire testing system can be seen in FIG. 1, taken from U.S. Pat. No. 5,481,907, the entirety of which is herein incorporated by reference.
FIG. 1 illustrates a tire testing system 10 incorporating an adjustable wheel positioning assembly 12. The adjustable wheel positioning assembly 12 is mounted and slides on rails 13 which in turn are fixed to a stationary frame 14. The adjustable wheel positioning assembly 12 supports a wheel assembly 16 against a road wheel 18. An outer perimeter surface 20 of the road wheel 18 contacts the tread of a tire 22 of the wheel assembly 16. The outer surface 20 simulates various road surfaces such as black top or concrete. Tire radial loads are applied using a suitable servohydraulically controlled hydraulic actuator, attached to the adjustable wheel positioning assembly 12 and the frame 14. The adjustable wheel positioning assembly 12 adjusts the position of the tire 22 on the outer surface 20. In the embodiment illustrated, the adjustable wheel positioning assembly 12 adjusts the slip angle or steer of the tire 22, which is the rotation of the tire 22 about an axis 24 in a direction indicated by double arrow 26, the axis 24 being generally perpendicular to the contact patch of the tire 22 with the road surface 20. In addition, the adjustable wheel positioning assembly 12 adjusts the camber angle of the tire 22 relative to the outer surface 20. As illustrated, the camber angle is pivotal displacement of the tire 22 and axis 24 on the road wheel 18 to and away from the frame 14 in a direction indicated by double arrow 30.
The frame 14 includes suitable cross members 32 such that the frame 14 self-reacts all forces applied to the tire 22 by the system so that a special facility foundation is not required. A drive/braking unit 38 rotates or loads the roadwheel 18 through a drive belt 40 applying power or braking loads selectively to the roadwheel 18. A direct drive or gear box would also be acceptable. A control system 44 having suitable analog and digital controls monitors system performance and provides command instructions to adjust speed of the roadwheel 18, positioning of the tire 22 on the roadwheel 18 by the adjustable positioning of assembly 12, and location of the adjustable wheel positioning assembly 12 on the frame 14. An operator control center 48 connected to the control system 44 through signal lines 50 provides an interface for an operator.
In a preferred embodiment, three additional adjustable tire positioning assemblies 52, 54 and 56 are provided to allow the system 10 to test four tires simultaneously. As illustrated, the adjustable wheel positioning assembly 52 is mounted to the frame 14 with slides, not shown, on a side opposite adjustable wheel positioning assembly 12. The adjustable wheel positioning assembly 52 supports a wheel assembly 60 so that a tire 62 mounted thereto contacts the roadwheel 18. The adjustable tire testing assemblies 54 and 56 are mounted to the frame 14 in a similar manner on opposite sides of a second roadwheel 64. The second roadwheel 64 is rotated or loaded by a drive/braking unit 66 similar to drive/braking unit 38. Flexible conduits 68, 70, 72 and 74 enclose data signal and control lines, not shown, allowing each of the adjustable tire testing assemblies 12, 52, 54 and 56, respectively, to move relative to the frame 14.
The present invention provides an advantage over the design shown in FIG. 1 by providing for lateral movement of the test tire over the surface of the road wheel. Moreover, one shortcoming of the illustrated design is the repeated use of the same circumferential surface area on the road wheel.